SAN FRANCISCO — San Francisco’s emergency water system is not adequate for putting out multiple fires at once during a major disaster like a strong earthquake, according to current and former fire officials.

In the decades since fires caused by a 1906 earthquake devastated the city, voters have approved hundreds of millions of dollars in bond money for an elaborate emergency water system. But the city has failed to spend it properly in recent decades, fire officials told the San Francisco Chronicle.

“We have an unlimited water supply, but no way to get it to the fires in half of the city,” said Thomas Doudiet, a retired San Francisco assistant deputy fire chief.

For example, the newspaper says San Francisco hasn’t spent enough to purchase the portable firefighting equipment that is instrumental to battling blazes in the city’s outer residential districts.

The system helped extinguish the large fire at a construction site in the city’s Mission Bay district earlier this month and was used to battle the Marina District blazes after the 1989 Loma Prieta earthquake.

The effort to remake the city’s emergency water system occurred after fires in 1906 destroyed 27,000 buildings. The blazes burned largely unimpeded due to poor water pressure.

City engineer Michael O’Shaughnessy designed a state-of-the-art, gravity-fed system with three large reservoirs built atop some of the city’s famous hills and augmented by giant pumps that could draw San Francisco Bay water.

Since then, the city has expanded into areas that weren’t covered by O’Shaughnessy’s engineering marvel, leading officials to build 200 underground storage tanks that hold 75,000 gallons apiece.

In the 1980s, retired assistant fire chief Frank Blackburn designed a portable pumping system that allowed firefighters to tap into these cisterns and shoot water at high pressure.

But the portable system hasn’t been expanded since the 1980s, and currently only three rigs are available to fight fires in the city, according to the Chronicle.

“If we had four major fires like we had (at Mission Bay), we would have an issue,” Assistant Deputy Chief Ken Lombardi said. “There is no doubt the (portable) system works — we need more of it to make it work for the whole city.”

The city needs about $18 million for new rigs and equipment to bring the system up to the level it needs to be, according to Doudiet.

So far, the city has only received $400,000 in federal grants for the project.

“We’ve got to have the full system in place before the earthquake hits, and we don’t know when that is going to happen,” he said.